iOS 9不会在旧屏幕上保留动画

I have an issue in my app in iOS 9. I have an animation on the first page of my app. It works fine for iOS 8 or earlier, but in iOS 9 phones when I go to next viewcontroller and come back to that viewcontroller animation stops. Here is my code.I have an issue in my app in iOS 9. I have an a